1. Field of the Invention
The present invention relates to a light source apparatus and a display apparatus.
2. Description of the Related Art
Among the color image display apparatuses are ones that have a color liquid crystal panel with a color filter and a light source apparatus (backlight apparatus) for irradiating the back of the color liquid crystal panel with white light. Fluorescent lamps such as cold cathode fluorescent lamps (CCFLs) have conventionally been used mainly as the light-emitting elements of the light source apparatuses. In recent years, however, light-emitting diodes (LEDs) have been increasingly used as the light-emitting elements of the light source apparatuses as they are excellent in terms of power consumption, life duration, color reproducibility, and environmental burden.
The light source apparatuses that use LEDs as the light-emitting elements (LED backlight apparatuses) generally have a large number of LEDs. Japanese Patent Application Publication No. 2001-142409 discloses an LED backlight apparatus having a plurality of light sources (light-emitting parts) each of which has one or more LEDs. Japanese Patent Application Publication No. 2001-142409 also discloses controlling the light emission brightness of each light source. By dropping the light emission brightness of the light sources that emit light to the regions on the screen of the color image display apparatus where a dark image is displayed, power consumption can be reduced, improving the contrast of the displayed image (the image displayed on the screen). This type of light emission control in accordance with the characteristics of an image is called “local dimming control.”
Suppressing the expansion of light emitted from each light source can enhance the level of improvement of the contrast through local dimming control. Specifically, suppressing a leak of light emitted from each light source to the regions corresponding to the other light sources can enhance the level of improvement of the contrast through local dimming control. Japanese Patent Application Publication No. 2009-103916 discloses a structure in which each light source is surrounded with a partition wall (described hereinafter as “individual partition structure”). The individual partition structure is also called “a structure in which each of the light sources is isolated from other light sources by the partition wall.” In the individual partition structure, the expansion (leak) of light emitted from the light sources can be suppressed because the partition wall can shield the light that is emitted from a light source to other light source.
On the other hand, a problem with the light source apparatuses is that the light emission characteristics of each light source change. Changes in the light emission characteristics occur due to, for example, changes in the temperatures of the light sources, time-related deterioration of the light sources, and the like. In a light source apparatus with a plurality of light sources, variations in the light emission characteristics of the plurality of light sources occur due to variations in the temperatures or levels of time-related deterioration of the plurality of light sources. This, as a result, causes variations in the light emission brightness of the plurality of light sources and variations in emission colors of the plurality of light sources. Variations in the light emission characteristics of the plurality of light sources cause the light source apparatus to generate uneven light. For instance, when the light emission brightnesses of the plurality of light sources fluctuate, the light source apparatus generates light of uneven brightness. When the emission colors of the plurality of light sources fluctuate, the light source apparatus generates light of uneven colors.
As a technique for reducing such changes in light emission brightnesses, changes in emission colors, uneven brightnesses and uneven colors, there is known a technique for adjusting light of a light source by using an optical sensor that detects the light emitted from the light source. Specifically, there is known a technique for adjusting light of a light source based on a detection value of an optical sensor that is provided to detect the light reflected off an optical sheet (optical member) of the light source apparatus at the light source side. A light source apparatus with a plurality of light sources performs a process of turning the light sources on sequentially and detecting reflected light to adjust the emitted light for each light source. Such technique is disclosed in, for example, Japanese Patent Application Publication No. 2013-211176.
It is preferred that the number of optical sensors and the number of processing circuits for processing the output signals of the optical sensors be low for the purpose of reducing the costs. For instance, instead of providing an optical sensor and a processing circuit with respect to each light source, it is preferred that an optical sensor and a processing circuit be provided for every two or more light sources.
However, when an optical sensor corresponding to two or more light sources is provided in a light source apparatus having the individual partition structure, the light moving from the light sources to the optical sensor is shielded by the partition wall. As a result, an adequate amount of light cannot enter the optical sensor, causing deterioration in the accuracy of detection of light emitted from the light sources.